Survival patterns in cystic fibrosis

Abstract

This paper describes the Data Registry System of the Cystic Fibrosis Foundation. Through this system an annual up-dated and corrected data base has been prepared for cystic fibrosis patients seen at U.S.A. Centers from 1966 through 1972. From the data base, a large number of life table studies are calculated. A study is specified by its data base, the observation period, analysis year (age year or year since diagnosis), the Centers included, and the condition of patients at birth, and possible additional factors such as sex, age at diagnosis, or race. The annual rates of mortality are measured by a force of mortality technique. Two techniques have been used to appraise the mortality of particular groups, graphing the cumulative survival function for the group together with the cumulative survival function for a comparison group, and calculation of mortality ratios of actual to expected deaths (by an applicable standard mortality table). This latter approach lends itself readily to tests of significance. For the purpose of calculating mortality ratios, two standard tables have been prepared on the basis of the 1972 Data Base and the 1966–1972 observations. The first of these standard tables is for use with age year studies, and the second is for years since diagnosis studies. The paper comments on a number of mortality studies by calendar year, by sex, by condition at birth, by age at diagnosis, and of survival from diagnosis of patients diagnosed in 1966–1972. The calendar year studies indicate an improvement trend in the survival experience from 1966 to 1972 but a change may be occurring. The study by sex exhibits a higher female mortality. The 7% of patients who have meconium ileus at birth show a significantly higher first-year mortality, and a somewhat lower survival rate thereafter even if the first year of life experience is excluded. Mortality data for groups specified by age at diagnosis are given. For patients diagnosed during 1966–1972, there is some indication of better survival than for patients diagnosed prior to 1966. The continuation of these mortality studies on an annual basis should further our understanding of survival patterns for cystic fibrosis patients.